This invention relates to a bearing assembly having means for sensing the rotational speed of a rotatable shaft; more particularly, it relates to bearing assemblies with inner and outer races having outwardly projecting flanges. The sensor assembly and encoder are mounted to the flanges so that the sensor is stationary and the encoder is mounted to the rotatable race. This invention is especially well-suited for use in the wheel bearings of automobiles.
As the automotive industry becomes more competitive, more emphasis is placed on getting better fuel economy and lowering the costs of material and labor. Wheel bearings are being modified to cost less, to be more compact in size, to be lighter in weight, and to provide more functions than existing components. With increased emphasis on anti-lock braking systems and suspension systems development, the wheel bearing is being looked at even more closely.
Prior art patents disclose structures which include a sensor assembly and an encoder-type component in a bearing assembly for use with an automobile wheel bearing assembly. An example of this type of prior art is included in U.S. Pat. No. 4,795,278 for a "Bearing Assembly" issued in the name of Yoshitaka Hayashi on Jan. 3, 1989. Other prior art patents disclose the incorporation of seals in the bearing assembly. An example of this type of prior art is disclosed in U.S. Pat. No. 3,772,549 for a "Wheel Speed Sensor" issued in the name of James C. Cumming on Nov. 13, 1973.
Other examples of the prior art are disclosed in the following U.S. Patents. U.S. Pat. No. 4,667,156 for a "Vehicle Wheel Bearing Mounted Pulser" issued in the names of Takami Machino Machino and Akira Kikuchi on May 19, 1987, discloses a geartooth configuration for the encoder, as well as several ways to mount the encoder to a bearing race. Also, U.S. Pat. No. 4,783,180 for a "Bearing Assembly For Vehicle" issued in the name of Yoshitaka Hayashi on Nov. 8, 1988, discloses an annular member (e.g., 54 in FIG. 1) on which an encoder component is mounted.
The primary problem with the prior art is that the addition of a sensor assembly and an encoder has been made at the expense of some of the other important factors discussed above. For example, some designs require additional axial bearing length relative to a wheel bearing with no speed sensing capability. Other bearing assembly/sensor assembly/ encoder configurations require relatively complex assembly procedures which tend to increase the labor costs associated with those wheel bearing designs. Some designs require a relatively elaborate adjustment of the position of the sensor assembly relative to the encoder in order to ensure a proper speed signal is provided. The prior art fails to disclose several bearing assembly/ sensor assembly/encoder configurations which are desirable from a manufacturing point of view, or for reasons of material and labor costs. Certain configurations which provide a minimal envelope, or volume, for the components are not disclosed.
The foregoing illustrates limitations know n to exist in present bearing assembly speed sensors. Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.
The bearing assembly of the present invention incorporates these advantages in unique configurations which combine a sensor assembly and encoder with a bearing assembly to optimize the envelope volume and minimize costs. Briefly described, the bearing assembly of this invention comprises a stationary race with an outwardly projecting flange, a rotatable race with an outwardly projecting flange, a sensor assembly mounted on the stationary race, and an encoder mounted on the rotatable race. The axial space between the two flanges is utilized as efficiently as possible. The configurations resulting from the various mounting means are unique relative to the prior art cited above, and provide substantial cost and size advantages over the prior art.